Other Non-Current Assets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Deferred contract costs, net of accumulated amortization	$ 161.3	$ 136.1
Property records database	59.9	59.7
Prepaid fees	18.3	4.0
Contract assets	17.0	0.0
Deferred compensation plan related assets	11.1	11.7
Unrealized gains on interest rate swaps	6.2	6.7
Unbilled receivables	5.0	14.6
Other	8.1	7.3
Other non-current assets	$ 286.9	$ 240.1